Looking for a specific material

  1. Hi,

    I am a student looking for a material for a project at school. I am currently studying mechanical engineering so the chemistry and materials aspect is a bit over my head.

    We're working on a concept to develop a more ergonomic chair and would like to find a material that would be comfortable to sit on.

    My vision would be a bunch of gel-like spheres that could be electrically stimulated and move around due to a current passed over them. Also maybe create heat as a by product. Basically a comfortable thing to sit on that would be able to vibrate a bit.

    I've been trying to find stuff online but my limited knowledge of gears and beams isn't helping too much.

    Any help would be greatly appreciated.
     
  2. jcsd
  3. Baluncore

    Baluncore 2,516
    Science Advisor

    Comfort comes from avoiding points of high pressure. That can be achieved by using a fluid in a shaped bag or cushion since it will distribute the load more evenly.

    If the fluid was your gel-like spheres then it should be free to flow. Unfortunately gel-like spheres will probably not flow well, as they may bed into each other and form clumps. Unless they contain gas bubbles, gels behave more like liquids with a fixed volume, so the only flexibility would come from changing the packing density by distortion of the spheres.

    For comfort, cooling is probably more important than heating. Warmth can be achieved by reducing the rate of body heat loss through the seat. Insulation is a better investment than the expenditure of energy. Temperature stabilisation suggests thermal transfer such as airflow through, or of the fluid.

    Maybe if the spheres were piezoelectric they could be made to vibrate at an ultrasonic frequency and so flow better. But a single point source of mechanical vibration would be able to overcome static friction between spheres, so there is probably no need for individual spheres to be local generators.

    Have you considered a low-tech solution such as a cushion full of jumping beans? To fully evaluate all possibilities you will need a committee to sit on.
     
  4. Astronuc

    Staff: Mentor

    One may wish to visit a furniture store, or the website of chair and bed manufacturers. I recently had to buy a mattress, and in the process, I was given a partial course on the underlying support structure of mattresses. The very nice (and expensive) ones had individual coils. Some were much more comfortable (softness at different thickness/depth), and they offered different levels of support/stiffness.
     
  5. You have listed this as your only criteria for design of the chair, but I ask more ergonomic than what?

    There must have been a deficiency in other chair models that you have pinpointed and hence selected as a criteria that your new design will address. By reading your post I have not been able to itemize which major deficiency you are attempting to improve upon. I see the words 'comfortable', 'heat', 'vibrate'. I might then conclude that you are attempting a design for a type of 'massage' chair, to be used for relaxation after work, or perhaps during, though I am unsure if such a conclusion is correct. Envisions of a dentists chair to calm the patient during procedures also comes to mind.

    If you are designing from a blank sheet of paper then there are several environments to consider in which chairs are used.
    Is it indoor, outdoor, work, home, fixed, mobile, office, warehouse? Other settings could be equally as important.

    Funtionality might include other aspects than just the act of sitting in the chair. As an example, a chair that one can take to an outdoor theatre needs to be collapsible for storage, sturdy when unfolded, light to carry by hand, easily cleaned, strong enough to support weight, in addition to being as comfortable as possible. Perhaps adding a drink holder would be an additional feature.

    While you do have an idea of what you want to accomplish, you have to go back and refer to, or make a list criteria for the design, and check off which ones are satisfied and modify the prototype of those which are not. Along the way criteria will change, some will be added and others removed. Design is a feedback loop on itself.

    Anyways, here is a long list of definitions of ergonomics.
    http://www.hfes.org/Web/EducationalResources/HFEdefinitionsmain.html

    Hope this helps.
     
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